Pneumatic tire equipped with an electronic member

ABSTRACT

A tire casing is equipped with a radiofrequency transponder and includes a crown, two sidewalls and two beads, each bead including at least one annular bead wire revolving around a reference axis, at least one annular carcass ply, coaxial with the reference axis anchored in the beads separating the tire casing into two zones, inside and outside the carcass ply. The radiofrequency transponder comprises at least one electronic chip and a radiating radiocommunication antenna and is positioned radially externally in relation to said bead wire, characterized in that the radiofrequency transponder comprises a primary antenna electrically connected to the electronic chip, in that the primary antenna is electromagnetically coupled to the radiating antenna, and in that the radiating antenna is formed by a strand helical spring defining a first longitudinal axis.

FIELD OF THE INVENTION

The present invention relates to a tyre casing equipped with anelectronic unit communicating with radiofrequency devices external tothe tyre casing.

TECHNOLOGICAL BACKGROUND

The development of electronic units integrated into mounted assemblies,comprising a tyre casing and a wheel, has intensified over the last fewyears. Specifically, these electronic units, such as radiofrequencytransponders or RFID (acronym for radiofrequency identification) tags,contain information on the mounted assembly, such as the identifier ofthe tyre casing, its characteristic dimensions, etc., which are crucialdata in the management and storage of such articles. In addition, theseelectronic units are also able to measure parameters of the mountedassembly such as, for example, the temperature inside the cavity formedby the tyre casing and the wheel rim in a mounted, inflated state. Theseparameters are essential to safe use of the mounted assembly.Communication with these electronic units, in particular in order tocommunicate the parameters of the mounted assembly, is generallyachieved by way of radiofrequency transmission to externaltransmitter/receiver devices.

Integrating such electronic units into the mounted assembly and inparticular into the tyre casing is not simple. Specifically, in order toensure the reliability of the information contained in these electronicunits and in particular the information regarding the identifier of thetyre casing throughout the cycle of the product, it is preferable forthe electronic unit to be securely fastened to the tyre casing for whichit contains identification information. Integrating such electronicunits into the structure of a tyre casing poses a certain number ofchallenges. Firstly, inserting an electronic unit into the structure ofthe tyre may lead to degradation of the tyre casing; it is thereforenecessary to ensure that the tyre casing keeps its physical integritythroughout its life cycle. The second relates to the radiocommunicationperformance of the electronic unit. Specifically, the complex structureof an assembly mounted with, in particular, its stacks of rubber blendsof different permittivities and its metal elements generate interferencein the radiofrequency operation of the antenna of the electronic unit,in particular in the UHF (acronym for ultra-high frequency) frequencyband. Lastly, the third challenge consists in ensuring the physicalintegrity of the electronic unit itself throughout the life cycle of thetyre casing, and in particular because of the high thermomechanicalstresses to which the tyre casing is subjected under running conditions.

Document EP1977912 A1 describes a preferred position of an electronicunit communicating through radiofrequency within a tyre casingarchitecture in order to improve the performance compromise between theradiocommunication quality of the electronic unit and the physicalintegrity both of the tyre casing and of the electronic unit. However,due to the constraints linked to the structural integrity of theelectronic unit subjected to the thermomechanical stresses generated bythe running of the tyre casing, the identified position, although itcorresponds to the best compromise, is not optimum in terms ofradiocommunication.

The aim of the invention is to identify the optimum positions forintegrating, into the tyre casing, an electronic unit, such as aradiofrequency transponder, with regard to its physical integritywithout impacting its radiocommunication performance, in particular inthe UHF band, or the endurance of the tyre casing. Of course, it shouldnot be necessary either to have to modify the main steps ofmanufacturing the tyre casing or its architecture.

DESCRIPTION OF THE INVENTION

The invention relates to a tyre casing equipped with an electronic unitand including a crown, two sidewalls and two beads. Each bead includesat least one annular bead wire revolving around a reference axis. Thetyre casing also includes at least one annular carcass ply, coaxial withthe reference axis anchored in the beads separating the tyre casing intotwo zones, inside and outside the carcass ply. The electronic unitcomprises at least one electronic chip and a radiatingradiocommunication antenna and is positioned radially externally inrelation to the bead wire. The tyre casing is characterized in that theelectronic unit comprises a primary antenna electrically connected tothe electronic chip, in that the primary antenna is electromagneticallycoupled to the radiating antenna, and in that the radiating antenna isformed by a strand helical spring defining a first longitudinal axis.

Integrating such an electronic unit thus makes it possible both toreduce the risks of deterioration of the electronic unit due to itsstructure, while at the same time improving the radiocommunicationperformance of the electronic unit and minimizing the risks linked tothe physical integrity of the tyre casing.

Specifically, deterioration of the electronic unit is generally causedby failures in the connections that exist between the communicationantenna and the electronic portion of the unit. Here, no mechanicalconnection is produced since the transfer of energy between thecommunication antenna and the electronic chip is achieved with anelectromagnetic field, via a primary antenna. However, although the sizeof the radiating antenna, which is linked to the communication frequencyband and to its far-field operation, is by nature large, the primaryantenna is not subjected to this constraint. It is thus of smaller size,in general allowing the deformations of the tyre casing to be easilyendured without generating excessively high mechanical stresses withinthe electrical junction between it and the electronic chip. Lastly,incorporating the electronic unit into various components of the tyrecasing protects the electronic unit from stresses external to themounted assembly during running or during the mounting of the tyrecasing on the wheel.

Secondly, the introduction of the primary antenna makes it possible todisassociate contradictory functions between the size of the radiatingantenna and the electrical impedance of the electronic portion of theunit. It is thus possible to dimension the primary antenna so as tomatch its electrical impedance to the chip in order to minimize lossesand to therefore improve the energy efficiency of the electronic unit.The dimensions of the radiating antenna are then chosen solely withrespect to the criterion of the communication frequency of theelectronic unit. All of this tends to improve the radiocommunicationperformance of the electronic unit.

In addition, the position of the electronic unit in a standard tyrecasing, far from the wheel of the mounted assembly and the bead wire,which is more often than not made of metal, minimize radiofrequencycommunication interference of the electronic unit.

In particular, the communication frequency of the electronic unit issituated in the ultra-high frequency (UHF) band of between 300 MHz and 3GHz, allowing an advantageous compromise to be obtained between a smallsize of the radiating antenna, which is easily able to be integratedinto a tyre casing, and a large distance from which the electronic unitis readable, this distance being far from the tyre casing.Advantageously, the electronic unit communicates in the narrow frequencyband of between 860 MHz and 960 MHz and more specifically in very narrowbands of 860 MHz to 870 MHz and 915 MHz to 925 MHz. Specifically, atthese frequencies, the conventional elastomer blends of the tyre casingconstitute a good compromise with respect to propagation of radio waves.In addition, these frequencies are the highest possible in order tominimize the size of the radiating antenna so as to facilitateintegration of the electronic unit into the tyre casing.

According to one preferred embodiment, the primary antenna is a coilhaving at least one turn defining a second longitudinal axis that iscircumscribed in a cylinder. The axis of revolution of the cylinder isparallel to the second longitudinal axis and the diameter is between athird and three times, preferably between half and two times, the meandiameter of the helical spring of the radiating antenna.

Thus, with the primary antenna being a loop antenna, energy is mainlytransferred between the radiating antenna and the primary antenna byinductive coupling. This then requires a certain proximity (in order tolimit the air gap between the two antennas) between the two antennas,requiring the coil of the primary antenna to be dimensioned, withrespect to the radiating antenna, in order to ensure a sufficient energytransfer efficiency by minimizing the air gap between the two coils inorder to obtain the desired radiocommunication quality.

In concrete terms, the primary antenna may advantageously have adiameter smaller than that of the radiating antenna; in this case theentirety of the electronic portion of the transponder is inserted intothe radiating antenna and the assembly is particularly robust in anenvironment such as that of a tyre.

The antenna may also have a diameter larger than that of the radiatingantenna; this case is particularly advantageous when it is desired toadd, to the radiofrequency transponder, other, active or passive,electronic components in order to perform additional functions, forexample monitoring of the state of the tyre.

According to one preferred embodiment, with the radiating antenna havinga central zone between two lateral zones and the primary antenna havinga median plane perpendicular to the second longitudinal axis, the firstand second longitudinal axes are parallel to one another and the medianplane of the primary antenna is arranged in the central zone of theradiating antenna.

The term “central zone” is here understood to mean the cylinder definedby the inside diameter of the helical spring situated on either side ofthe median plane of the helical spring and the height of whichcorresponds to 25% of the length of the helical spring, preferably 15%of the length of the helical spring.

It is thus ensured that the distance between the radiating and primaryantennas is constant along the longitudinal axes of these antennas, thusoptimizing, at each element having a length of the primary antenna, anequivalent transfer of energy. In addition, with the magnetic fieldcreated by a coil through which an electric current flows being at amaximum in the central zone of the coil, it is preferable to positionthe median plane of the primary antenna in this central zone of theradiating antenna in order to maximize the magnetic field at the originof the electromagnetic coupling.

According to one particular embodiment, with the carcass ply havingcords that are parallel to one another, the first longitudinal axis ofthe electronic unit is oriented perpendicular in relation to the cordsof the carcass ply.

Better integrity of the electronic unit and in particular of theradiating antenna is thus ensured. The latter may bear on the cords ofthe carcass ply, which is a reinforcing ply essential to the structuralstrength of the architecture of the tyre casing due to its geometricproximity to the cords. In addition, the shape of the radiating antennapositioned in this way makes it possible to withstand thethermomechanical stresses of the tyre casing during running, inparticular at the time of passing into the contact area. In particular,the radiating antenna deforms elastically due to its helical springshape at the time of the deradialization of the cords of the carcass plywhen passing through the contact area. In addition, when the cords ofthe carcass ply are metal in nature, these are liable to generateinterference with respect to the propagation of radio waves. Theposition of the radiating antenna perpendicular to the cords limits thisinterference.

According to one particular embodiment, with the carcass ply having aportion folded around the bead wire, with the free edge of the foldedportion of the carcass ply being situated radially between the referenceaxis and the electronic unit and in the zone of the tyre casing in whichthe electronic unit is located, the electronic unit is spaced from thefree edge of the carcass ply by at least 10 mm, preferably by at least15 mm.

The desired technical effect is a spacing from the free edge of thecarcass ply, which constitutes a structural singularity within thestructure of the tyre casing. Specifically, the radial rigidity of thisply is by nature far greater than that of the rubbers, which representmost of the volume of a tyre casing. Thus, by ensuring a distance to theelectronic unit, which is also by nature a rigid object in comparisonwith the rubbers, the risk of deterioration of the tyre casing at thesesingularities is limited, by limiting stress concentration phenomena,thereby preserving the integrity of the architecture of the tyre casing.Depending on the rigidity of the rubber masses close to this free edgeand to the electronic unit, it is necessary to define the correctspacing between the two singularities.

According to one particular embodiment, with the tyre casing comprisinga first annular rubber mass, coaxial with the reference axis, situatedradially between the reference axis and the electronic unit, with a freeedge situated in the zone of the tyre casing in which the electronicunit is located, the electronic unit is spaced from the radially outerfree edge of the first rubber mass by at least 5 mm, preferably by atleast 10 mm.

If the elastic modulus of the first rubber mass is rigid with respect toanother rubber mass of the architecture of the tyre that is adjacentthereto, the end of this first rubber mass then constitutes a structuralsingularity of the tyre casing. For example, this first rubber mass isthe filler rubber situated adjacent and radially externally in relationto the bead wire. Any structural singularity is a source of mechanicalstress concentration that is favourable to possible cracking due tofatigue that is detrimental to the integrity of the structure. It isthus preferable to space the electronic unit, which is also a structuralsingularity in the architecture of the tyre casing, in order to limitthe excessively high levels of mechanical stress at these singularitiesand preserve the structural integrity of the tyre casing. Depending onthe rigidity of the rubber masses close to this free edge and to theelectronic unit, it is necessary to define the correct spacing betweenthe two singularities.

According to one particular embodiment, with the tyre casing comprisinga first annular reinforcing ply, coaxial with the reference axis,situated radially between the reference axis and the electronic unit,with a free edge situated in the zone of the tyre casing in which theelectronic unit is located, the electronic unit is spaced from theradially outer free edge of the first reinforcing ply by at least 10 mm,preferably by at least 15 mm.

The radially outer free edge of the first reinforcing ply thusrepresents a mechanical singularity particularly susceptible to stressconcentrations. Spacing the electronic unit, which also represents amechanical singularity due to its rigidity, limits the stressconcentrations in this zone. The mechanical endurance of the tyre casingis thus thereby improved. This is particularly true depending on thenature of the cords of the first reinforcing ply and their orientationwith respect to the free edge of the first reinforcing ply, therebymaking it necessary to adjust the spacing between the two singularities.

According to one particular embodiment, the tyre casing comprises asecond annular rubber mass, coaxial with the reference axis, situatedradially externally to the electronic unit with respect to the referenceaxis, with a free edge in the zone in which the electronic unit islocated, the electronic unit is spaced from the radially inner free edgeof the second rubber mass by at least 5 mm, preferably by at least 10mm.

If the elastic modulus of the second rubber mass is rigid with respectto another rubber mass of the architecture of the tyre that is adjacentor close thereto, the end of this first rubber mass then constitutes astructural singularity of the tyre casing. Any structural singularity isa source of mechanical stress concentration that is favourable topossible cracking due to fatigue that is highly detrimental to theintegrity of the structure. It is thus preferable to space theelectronic unit, which is a structural singularity in the architectureof the tyre casing, in order to limit the excessively high levels ofmechanical stress in this zone and preserve the structural integrity ofthe tyre casing.

According to one particular embodiment, the tyre casing comprises asecond annular reinforcing ply, coaxial with the reference axis,situated radially externally to the electronic unit with respect to thereference axis, with a free edge situated in the zone in which theelectronic unit is located. The electronic unit is spaced from theradially inner free edge of the second reinforcing ply by at least 10mm, preferably by at least 15 mm.

The radially inner free edge of the second reinforcing ply thusrepresents a mechanical singularity particularly susceptible to stressconcentrations. Spacing the electronic unit, which also represents amechanical singularity due to its rigidity, limits the high stressconcentrations in this zone. The mechanical endurance of the tyre casingis thus thereby improved. This is particularly true depending on thenature of the cords of the second reinforcing ply and their orientationwith respect to the free edge of the second reinforcing ply, therebymaking it necessary to adjust the spacing between the two singularities.

According to one particular embodiment, the tyre casing comprises athird annular reinforcing ply, coaxial with the reference axis, situatedat least partly in the crown, delineated by two free edges. Theelectronic unit is situated axially between the two free edges of thethird reinforcing ply. This third reinforcing ply comprises metal cordswhose main direction is not parallel to the reference axis. Theelectronic unit is radially spaced from the third reinforcing ply by atleast 5 mm.

The third metal reinforcing ply situated in the crown is thus liable tointerfere with the radiocommunication of the electronic unit alsosituated in the crown, in particular if the metal reinforcers are notoriented perpendicular to the axis of the primary antenna of theelectronic unit. The spacing of the electronic unit from the metal zonesminimizes the radiocommunication interference of the electronic unit.This spacing is proportional to the active electromagnetic field zone ofthe primary antenna.

According to one preferred embodiment, the electronic unit isencapsulated in at least one electrically insulating encapsulatingrubber mass.

Manipulation of the electronic unit during the step of manufacturing thetyre casing is thus facilitated, in particular so as to ensure preciseand certain positioning of the electronic unit within the tyre casing.Specifically, the electronic unit comprises electronic components andradiocommunication components made primarily of metal or plastic, forwhich adhesion to a rubber mass is not natural. Using an encapsulatingmass that is able to be applied outside of the manufacturing chain ofthe tyre casing makes it possible to create a rubber/rubber interfacethe adhesion of which is often facilitated. Lastly, the termelectrically insulating is understood to mean that the electricalconductivity of encapsulating rubber is below the conductive chargetransfer threshold of the blend.

According to one preferred embodiment, the elastic modulus of theencapsulating rubber mass is lower than or equal to the elastic modulusof the adjacent rubber blends.

The term “elastic modulus” is understood here to mean the modulusobtained when applying a uniaxial extension stress of 10% after anaccommodation cycle and at a temperature of 22° C.

The rigidity of the encapsulating mass is thus lower than or equal tothe rigidity of the adjacent rubber blends. Due to this, thisencapsulating rubber will deform under mechanical stress, withouttransmitting excessively high forces to the electronic unit. This tendsto improve the mechanical endurance of the electronic unit.

According to one highly preferred embodiment, the relative dielectricconstant of the encapsulating rubber mass is lower than the relativedielectric constant of the adjacent rubber blends.

Generally speaking, the higher the dielectric constant of the rubbermass encapsulating the unit, the more attenuated the electrical signalreceived and transmitted by the electronic unit. For rubber blends ofthe tyre casing that are not electrically insulating, the relativedielectric constants may reach levels of 10 and even more in the UHF(acronym for ultra-high frequency) range. The radiocommunicationperformance of the electronic unit is greatly improved if the dielectricconstant of the encapsulating mass is lower than the dielectricconstants of the adjacent rubbers having high permittivity (>10). Therelative dielectric constant of the encapsulating mass is preferablylower than 6.5 and very preferably lower than 4.5 in the UHF frequencyrange.

The term electrically insulating is understood here to mean that theelectrical conductivity of the rubber is below the conductive chargetransfer threshold of the blend.

Advantageously, the electronic unit is a radiofrequency transponder.

The electronic unit is thus interrogated passively from outside theelectronic unit. The phases of interrogation of the electronic unit thendo not require any power specifically from the electronic unit. Thefunctionality of the radiofrequency transponder is primarily a role ofidentifying the tyre casing.

The electronic unit preferably also comprises one or more passive oractive electronic components.

The electronic unit thus increases its functionalities by way of theseadditional components. The active components potentially supply thepower necessary for the operation of the additional components. Thepower source may be for example a battery or a piezoelectric component.These components may also be an accelerometer or a temperature sensor.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood upon reading the followingdescription, given solely by way of nonlimiting example and withreference to the appended figures, throughout which the same referencenumerals denote identical parts, and in which:

FIGS. 1 and 2 are perspective views of a radiofrequency transponderaccording to one of the subjects of the invention;

FIG. 3 is a perspective exploded view of a radiofrequency transponderencapsulated in an encapsulating rubber mass;

FIG. 4 is a view in meridian section of a portion of a tyre casing;

FIG. 5 is a view in meridian section of the bead of a tyre casing whenthe electronic unit is located in the outer zone of the tyre casing;

FIG. 6 is a view in meridian section of the bead of a tyre casing whenthe electronic unit is located in the inner zone of the tyre casing;

FIG. 7 is a view in meridian section of the portion of a tyre casingwhen the electronic unit is located on the sidewall of the tyre casing;and

FIG. 8 is a view in meridian section of a portion of the tyre casingwhen the electronic unit is located at the crown of the tyre casing.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 1 shows a radiofrequency transponder 100 in a configuration inwhich the electronic portion 120 comprising the electronic chip 101 andthe primary antenna 107 is situated inside the radiating antenna 102.This configuration allows a space saving for the radiofrequencytransponder 100, which is rather intended to be incorporated into thebead or the sidewall of a tyre casing. The geometric shape of theelectronic portion 120 is circumscribed in a cylinder the diameter ofwhich is smaller than or equal to the inside diameter 104int of thehelical spring forming the radiating antenna 102. It is thus firstlyensured that the air gap between the two antennas is small. In addition,it is ensured that the electronic portion 120 is held with respect tothe radiating antenna 102, making it possible to have the same energytransfer efficiency between the two antennas over the entire length ofthe primary antenna 107. Lastly, the threading of the electronic portion120 into the radiating antenna 102 is facilitated thereby. The medianplane of the primary antenna 107 is located in the central zone of theradiating antenna 102 so as to maximize the electromagnetic couplingbetween the two antennas.

The electronic portion 120 comprises, in this example, an electronicchip 101 and a primary antenna 107 that is electrically connected to theelectronic chip 101 by way of a printed circuit board. The primaryantenna 107 consists here of a surface-mount-device (SMD) microcoilhaving an axis of symmetry. The median plane of the primary antennadefined by a normal parallel to the axis of symmetry of the SMD coil andseparating the coil into two equal portions is determined. Thecomponents on the printed circuit board are electrically connected usingcopper tracks terminated by copper pads. The components on the printedcircuit board are electrically connected using the wire-bondingtechnique by gold wires having a diameter of 20 micrometres runningbetween the component and the pads. The assembly consisting of theprinted circuit board of the electronic chip 101 and of the primaryantenna 107 is embedded, using glob top technology, in a rigid mass 130made of electrically insulating high-temperature epoxy resin, formingthe electronic portion of the radiofrequency transponder. Of course,other configurations may be implemented. For example, the electricallyinsulating rigid mass may encapsulate just the electronic chip and aportion of the primary antenna.

The radiating antenna 102 consists of a steel wire with an outsidediameter of 200 micrometres that has been plastically deformed so as toform a helical spring with an outside diameter of the order of 1.4millimetres, having an axis of revolution defining the firstlongitudinal axis 103. The helical spring is primarily defined by awinding diameter of the coated wire and by a helix pitch. Thus, giventhe diameter of the wire, the inside and outside diameters of thehelical spring are precisely determined. The length of the spring, ofbetween 35 and 55 mm, corresponds here to the winding of a straight wireof a length equal to half the wavelength of the transmission signal ofthe radiofrequency transponder in an elastomer blend mass at 915 MHz. Itis thus possible to define the central zone of the helical springcorresponding to around 25% of the length of the spring, and preferably15%. This central zone is centred on the median plane of the helicalspring.

FIG. 2 shows a radiofrequency transponder 100 in a configuration inwhich the electronic portion 120 is located outside the radiatingantenna 102. The geometric shape of the electronic portion has acylindrical cavity 200 the diameter of which is larger than or equal tothe outside diameter of the radiating antenna 102. The threading of theradiating antenna 102 into the cylindrical cavity 200 of the electronicportion is thus facilitated thereby. The median plane of the primaryantenna 107 is located substantially in the central zone of theradiating antenna 102. This type of radiofrequency transponder will beof greater benefit in zones such as the crown of a tyre casing or theradially outer portion of the sidewall. Specifically, the electronicportion in this configuration may easily incorporate additional sensors,such as an accelerometer, or a battery, without otherwise impacting thetransfer of energy between the two antennas. The constraint of such asolution is the volume occupied by the radiofrequency transponder 100,which is far bulkier than the first configuration.

In a first step of producing the electronic portion of theradiofrequency transponder 100, using the conventional ultrasoundtechnique from the microelectronics industry, an electronic chip 101 andpossibly additional components are connected to a flexible support 136forming the printed circuit board (“Flex PCB”) so as to form theelectronic card. The electrical impedance of the electronic card ismeasured by way of an appropriate electrical apparatus, such as animpedance meter, across the terminals of the copper connections on thetop face of the flexible printed circuit board where the primary antennawill be connected. Each of the copper connections has a central cavitypassing through the thickness of the flexible support as far as thebottom face of the support.

In a second step, the primary antenna 107 is produced around a tube madeof electrically insulating resin whose inside diameter, delineating thecylindrical cavity 200 of the electronic portion, is larger than orequal to the outside diameter of the helical spring of the radiatingantenna 102, that is to say of the order of 1.5 millimetres. Thethickness of this tube is around 0.5 millimetres. Each end of the tubehas an excess thickness of 0.5 millimetres, forming an edge 138 of awidth of less than or equal to 0.5 millimetres.

A copper wire with a diameter of 200 micrometres is wound on the outerface of the tube, between the two edges, so as to form a given number ofturns, thereby making it possible to produce a primary antenna 107 inthe form of a cylindrical coil having an electrical impedance matched tothe impedance of the electronic card to which it will be electricallyconnected.

The flexible printed circuit board 136 of the electronic card producedin the first step is fastened to the edges 138 of the tube made ofinsulating resin using H20E conductive adhesive from Tedella. Each ofthe ends of the copper wire of the primary antenna 107 was insertedbeforehand between an edge 138 of the tube and the flexible printedcircuit board 136, the two portions to be assembled.

Lastly, an electrical connection is produced by welding a copper metalconductor through the cavity passing through the flexible printedcircuit board 136 at the copper connections. The electronic deviceconsisting of the electronic chip 101 and of the primary antenna 107 isthus produced.

In the last step, the electronic device is coated with an electricallyinsulating rigid mass 130 over a thickness of at least 1 millimetre inorder to protect the electronic card, containing the electronic chip101, and the primary antenna 107 from various chemical attacks and tomechanically protect the electrical connections. An injection techniqueis used that consists in positioning the electronic device in a mould.However, to preserve the cylindrical cavity 200 of the initial tube madeof resin, a flexible and air-impermeable membrane made of elastomer andpassing through the cylindrical cavity 200 is installed, which ispressurized in order to hermetically seal this cylindrical cavity 200against the propagation of the protective resin. The pressurizedinjection, at a pressure lower than that of the impermeable membrane, inthe liquid state of a high-temperature epoxy resin, such as theResolcoat 1060ES7 resin from Resoltech, is performed. This method allowsa homogeneous diffusion of the resin over the entire electronic device,except for the cylindrical cavity 200. After opening the mould andstopping the pressurization of the flexible membrane, the electronicdevice, still having the cylindrical cavity 200, but this time coatedexternally with a rigid mass made of electrically insulating resin, isextracted. The assembly represents the electronic portion 120 of theradiofrequency transponder 100.

The radiating antenna 102 is then introduced into the cavity 200 of theelectronic portion 120, such that the median plane of the electronicportion 120 corresponding to the median plane of the coil is situated inthe central zone of the radiating antenna 102. The threading of thehelical spring into the cavity 200 in fact ensures coaxiality of thefirst longitudinal axis 103 with respect to the second longitudinal axis108. The assembly ensures an optimum transfer of energy between the twoantennas.

FIG. 3 shows a radiofrequency transponder 100 embedded in a flexiblemass 112 made of electrically insulating elastomer, represented by theplates 112 a and 112 b of dimensions dependent on that of the radiatingantenna 102, and a thickness of for example between 2 and 5 millimetres.This radiofrequency transponder 100 is intended for example to beintroduced into the bead close to the bead wire filler rubber that isadjacent and radially external to the annular bead wire. Theradiofrequency transponder 100 here is in a configuration in which theelectronic portion 120 is situated inside the radiating antenna 102,thereby making it possible to miniaturize the electronic unit as much aspossible. The flexible mass 112 has an elastic modulus of the order of3.2 MPa and a relative dielectric permittivity of less than 6.5.

FIG. 4 shows a meridian section of a tyre casing 1 including a crown 82reinforced by a crown reinforcement or belt 86, two sidewalls 83 and twobeads 84. Each of these beads 84 is reinforced with a bead wire 85. Thecrown reinforcement 86 is surmounted radially on the outside by a rubbertread 89. A carcass reinforcement 87 anchored in the beads 84 separatesthe tyre casing into two zones, which will be called inner zone in thedirection of the fluid cavity and outer zone towards the outside of themounted assembly. The carcass reinforcement 87 is wound around the twobead wires 85 in each bead 84. The fold 88 of this reinforcement 87 isarranged here towards the outside of the tyre casing 1. In a mannerknown per se, the carcass reinforcement 87 consists of at least one plyreinforced by what are known as “radial” cords, here for example oftextile, that is to say that these cords are arranged virtually parallelto one another and extend from one bead to the other so as to form anangle of between 80° and 90° with the median circumferential plane EP.An airtight inner liner 90 extends from one bead to the other radiallyinternally with respect to the carcass reinforcement 87.

FIG. 5 shows a detailed view of the tyre casing 1 at the bead 84. Thisfigure illustrates the position of the radiofrequency transponder 100 inthe outer zone of the tyre casing 1 with respect to the carcass ply 87.

The bead 84 consists of the bead wire 85, around which the carcass ply87 is wound, with a folded portion 88 situated in the outer zone of thetyre casing 1. The folded portion 88 of the carcass ply 87 ends with afree edge 881. A rubber mass 91, called bead wire filler, is situatedradially externally and adjacent to the bead wire 85. It has a radiallyouter free edge 911 bearing on a face of the carcass ply 87 (moreprecisely on the outer calendering of the carcass ply, there is nodirect contact between the cords of the carcass ply and the electronicunit). A second rubber mass 92, called “reinforcing filler”, is adjacentthereto. It has two free edges. The first free edge 921 is situatedradially internally and bears on the folded portion 88 of the carcassply. The other free edge 922 is situated radially externally and ends onthe face of the ply of the carcass ply 87. Lastly, the sidewall 83covers both the reinforcing filler 92 and the carcass ply 87. Thesidewall has a free edge 831 situated radially internally and ending onthe folded portion 88 of the carcass ply.

The airtight inner liner 90, which is adjacent to the carcass ply 87 inthis configuration, is located on the inner zone of the tyre casing 1.It ends with a free edge 901 adjacent to the carcass ply 87. Lastly, aprotective bead 93 protects the carcass ply 87 and the radially innerends 901, 921 and 831 of the airtight inner liner 90, of the reinforcingfiller rubber 92 and of the sidewall 83, respectively. The outer face ofthis protective bead 93 is able to be in direct contact with the rimflange when mounting the tyre casing on the wheel. This protective bead93 has two radially outer free edges. The first free edge 931 issituated in the inner zone of the tyre casing 1. The second free edge932 is situated in the outer zone of the tyre casing 1.

The bead 84 of this tyre casing is equipped with two radiofrequencytransponders 100 and 100 a that are situated in the outer zone of thetyre casing 1. The first radiofrequency transponder 100, having beenencapsulated beforehand in an electrically insulating encapsulatingrubber, is positioned on the outer face of the bead wire filler 91. Itis positioned at a distance of 20 mm from the free edge 881 of thefolded portion 88 of the carcass ply that constitutes a mechanicalsingularity. This positioning ensures a zone of mechanical stability forthe radiofrequency transponder 100 that is beneficial to the mechanicalendurance thereof. In addition, embedding it within the structure of thetyre casing 1 gives it good protection against mechanical attacks comingfrom outside the tyre.

The second radiofrequency transponder 100 a, having been encapsulatedbeforehand in an electrically insulating encapsulating rubber compatiblewith or similar to the material of the sidewall 83, is positioned on theouter face of the sidewall. The material similarity between the sidewall83 and the encapsulating rubber ensures that the radiofrequencytransponder 100 a is installed inside and at the periphery of thesidewall 83 during the curing process. The radiofrequency transponder100 a is simply placed on the uncured outer face on the sidewall 83during the production of the tyre casing 1. Pressurizing the green bodyin the curing mould ensures the positioning of the radiofrequencytransponder 100 a in the cured state, as shown. This radiofrequencytransponder 100 a is situated far from any free edge of a rubbercomponent of the tyre casing. In particular, it is spaced from the freeedge 932 of the protective bead, from the free edge 881 of the carcassply and from the free edges 911 and 922 of the filler rubbers. Itsposition at the upper portion of the bead ensures improved communicationperformance with an external radiofrequency reader. Cyclic stressesduring running will not be disruptive due to the mechanical decouplingbetween the radiating antenna and the electronic portion.

FIG. 6 shows a detailed view of a tyre casing 1 at the bead 84. Thisfigure illustrates the position of the radiofrequency transponder 100 inthe inner zone of the tyre casing 1 with respect to the carcass ply 87.

The tyre casing comprises, in particular at the inner zone, an airtightinner liner 90 and a ply or a carcass inner reinforcing liner 96inserted between the carcass ply 87 and the airtight inner liner 90.This carcass inner reinforcing component 96 has a radially lower freeedge 961 located underneath the bead wire 85.

The location of the radiofrequency transponder 100 at the interfacebetween the airtight inner liner 90 and the carcass inner reinforcer 96allows the radiofrequency transponder 100 to be mechanically stabilized.Said radiofrequency transponder is about 40 millimetres above the freeedge 931 of the protective bead 93 that constitutes a mechanicalsingularity due to the high rigidity of the protective bead 93 incomparison with the airtight inner liner 90 and with the carcass innerreinforcer 96. By contrast, in order to ensure suitableradiocommunication performance, it is essential to use an encapsulatingrubber for the radiofrequency transponder 100 that is electricallyinsulating, and to place the first longitudinal axis of the radiatingantenna perpendicular to the cords of the carcass ply. From a mechanicalendurance point of view, this location is ideal for the electronic unit,which is protected from any external mechanical attack and from anyinternal thermomechanical attack.

The second location of the radiofrequency transponder 100 a according tothe invention allows improved radiocommunication performance by beingplaced higher in the bead 84. However, it should be encapsulated in anelectrically insulating rubber and the first longitudinal axis of theradiating antenna should be positioned perpendicular to the cords of thecarcass ply 87. Here, in this example, the first longitudinal axis isplaced circumferentially. However, it is preferable to avoid the centralzone of the sidewall, which is the zone that is the most mechanicallystressed.

FIG. 7 shows a view in meridian section of a tyre casing 1 correspondingto the installation of the radiofrequency transponder 100 on thesidewall 83 of the tyre casing 1. In this example, the radiofrequencytransponder 100 is installed substantially half way up the height of thesidewall 83 of the tyre casing 1, symbolized by the dashed line. This isan ideal zone in terms of radiocommunication, since it is first of allspaced from the large metal zones of the mounted assembly 1 whileoffering a free space on the outside of the mounted assembly. Inaddition, the surrounding rubbers are flexible rubbers generallysubjected to little load, which is favourable to good radiofrequencyoperation of the radiofrequency transponder 100. With regard to thephysical integrity of the electronic unit, even though this geometriczone is subjected to great cyclic stress in particular when passing intothe contact area, the mechanical decoupling of the radiating antennafrom the electronic portion allows a satisfactory lifetime of theradiofrequency transponder 100. With regard to the physical integrity ofthe tyre casing 1, the radiofrequency transponder 100 should be placedfar enough from the free edge 881 of the folded portion 88 of thecarcass ply 87, which is in this case located in the outer zone of thetyre casing 1. Spacing from the free edge 911 of the rigid rubbermasses, such as the bead wire filler rubber 91, is also desirable. Bybearing on the carcass ply 87, it is necessary, after havingencapsulated it in an electrically insulating encapsulating mass ifrequired, to place the first longitudinal axis of the electronic unitperpendicular to the cords of the carcass ply 87, which amounts toplacing it circumferentially in the case of a tyre casing 1 with aradial structure.

The second position on the sidewall 83 amounts to positioning theradiofrequency transponder 100 a on the outer face of the sidewall byencapsulating it in a rubber similar to that of the sidewall 83. Theadvantage of this position is the material homogeneity around theelectronic unit, which improves the radiocommunication performance ofthe radiating antenna. In order to meet the constraints linked to theintegrity of the tyre casing 1, the radiofrequency transponder 100 ashould be spaced from any free reinforcing ply edge or rubber masssituated in the outer zone of the tyre casing 1 with respect to thecarcass ply 87. Care will be taken in particular to space theradiofrequency transponder 100 a from the free edge 891 of the tread 89by at least 5 millimetres. Likewise, the radiofrequency transponder 100a will be spaced from the free edge 881 of the folded portion 88 of thecarcass ply 87 by at least 10 millimetres. Of course, the physicalintegrity of the radiofrequency transponder 100 a will be all the moreensured the further the radial position thereof is from the equator,corresponding to the axial ends of the mounted assembly, which are zonessusceptible to impacts with road equipment, such as pavement edges.Other positions, not illustrated in the drawings, are possible inparticular on the inner zone of the tyre casing 1 with respect to thecarcass ply 87. The inner zone of the tyre casing constitutes a naturalprotective zone for the electronic unit which is beneficial to thephysical integrity thereof, at the expense of slightly reducedradiocommunication performance. This inner zone also has the advantageof limiting the number of free edges of components of the tyre casingthat are potentially weak points with respect to the mechanicalendurance of the tyre casing equipped with an electronic unit.

FIG. 8 shows a view in meridian section of a tyre casing 1 correspondingto the installation of the radiofrequency transponder 100 at the crown82 of the tyre casing 1. The tyre casing 1 in this example comprises acrown reinforcement 86 formed by two metal reinforcing plies oriented at25 degrees with respect to the reference axis, one in the clockwisedirection and the other in the anticlockwise direction. The tyre casing1 also comprises an elastomer foam component 620 intended to damp cavityresonant noise. This foam 620 takes the form of a ring of rectangularcross section about the reference axis of the tyre casing 1. The crosssection of the ring comprises two faces 621 and 622 that arerespectively situated radially externally and internally with respect tothe reference axis. These two faces linked to one another by two axialedges 623 and 624 form a thickness of the order of 5 millimetres. Thiscomponent 620 is fastened, by conventional adhesion means, on theradially lower face of the airtight inner liner 90 of the tyre casing inthe cured state on the radially outer face 621. The radiofrequencytransponder 100 is fastened on the radially lower face 622 by any typeof chemical adhesion means, such as polyurethane, silicone,cyanoacrylate or silanized polyether adhesives. The radiofrequencytransponder 100 is thus sufficiently radially spaced from the metalreinforcing plies so as not to be subjected to interference duringradiofrequency operation thereof. In addition, it is also spaced fromany free edge of a rubber component of the tyre casing 1. Lastly,damping the component 620 preserves any excessively high transfer ofenergy to the radiofrequency transponder 100. The benefit of thisposition is that of indiscriminately allowing communication of theradiofrequency transponder 100 via both sidewalls 83 of the tyre casing1. This is convenient so as no longer to integrate the electronic uniton the outer or inner side of the mounted assembly, depending on theuse. It is possible to orient the axis of the electronic unit axially orcircumferentially.

Other positions of the radiofrequency transponder at the crown 82 arepossible, although not illustrated in the appended figures. For example,when the tread 89 is formed by two radially superimposed elastomerblends having different functions and material properties. Incorporatingthe radiofrequency transponder at the interface between these twomaterials firstly ensures sufficient spacing of the electronic unit withrespect to the metal reinforcing plies 86 of the crown 82. Reading fromoutside the tread 89 is also facilitated. For considerations of theability of the electronic unit to withstand heat, the position of theradiofrequency transponder to the right of a longitudinal channel wouldthen be preferable for the lifetime of the component and the integrityof the tyre casing.

Another alternative would be to place the radiofrequency transponder 100on the radially lower face of a self-sealing rubber blend layer situatedon the airtight inner liner 90 to the right of the tread 89. This layerhas good rubber/rubber adhesive properties and offers a sufficientradial thickness to ensure sufficient spacing between the electronicunit and the metal reinforcing plies.

The position of the radiofrequency transponder 100 on the inner or outerzone of the tyre casing 1 with respect to the carcass ply 87 is thuspossible even at the crown 82.

The invention claimed is:
 1. A tire casing equipped with aradiofrequency transponder and including a crown, two sidewalls and twobeads, each bead including at least one annular bead wire revolvingaround a reference axis, at least one annular carcass ply, coaxial withthe reference axis anchored in the beads separating the tire casing intotwo zones, inside and outside the at least one annular carcass ply, andthe radiofrequency transponder comprising at least one electronic chipand a radiating radiocommunication antenna and being positioned radiallyexternally in relation to the at least one bead wire, wherein theradiofrequency transponder comprises a primary antenna electricallyconnected to the electronic chip, wherein the primary antenna iselectromagnetically coupled to the radiating antenna, wherein theradiating antenna is formed by a strand helical spring defining a firstlongitudinal axis, and wherein the primary antenna is a coil having atleast one turn defining a second longitudinal axis that is circumscribedin a cylinder, an axis of revolution of which is parallel to the secondlongitudinal axis and a diameter of which is between a third and threetimes a mean diameter of the strand helical spring of the radiatingantenna.
 2. The tire casing according to claim 1, wherein the diameterof the cylinder is between half and two times the mean diameter of thehelical spring of the radiating antenna.
 3. The tire casing according toclaim 1, wherein, with the radiating antenna having a central zonebetween two lateral zones and the primary antenna having a median planeperpendicular to the second longitudinal axis, the first and secondlongitudinal axes are parallel to one another and the median plane ofthe primary antenna is arranged in the central zone of the radiatingantenna.
 4. The tire casing according to claim 1, wherein, with the atleast one annular carcass ply having cords that are parallel to oneanother, the first longitudinal axis of the radiofrequency transponderis oriented perpendicularly in relation to the cords of the at least oneannular carcass ply.
 5. The tire casing according to claim 1, wherein,with the at least one annular carcass ply having a portion folded aroundthe at least one bead wire, with the free edge of the folded portion ofthe at least one annular carcass ply being situated radially between thereference axis and the radiofrequency transponder and in the zone of thetire casing in which the radiofrequency transponder is located, theradiofrequency transponder is spaced from the free edge of the at leastone annular carcass ply by at least 10 mm.
 6. The tire casing accordingto claim 1, wherein, with the tire casing comprising at least one firstannular rubber mass, coaxial with the reference axis, situated radiallybetween the reference axis and the radiofrequency transponder, with atleast one edge situated in the zone of the tire casing in which theradiofrequency transponder is located, the radiofrequency transponder isspaced from the at least one radially outer edge of the at least onefirst annular rubber mass by at least 5 mm.
 7. The tire casing accordingto claim 1, wherein, with the tire casing comprising at least one firstannular reinforcing ply, coaxial with the reference axis, situatedradially between the reference axis and the radiofrequency transponder,with at least one edge situated in the zone of the tire casing in whichthe radiofrequency transponder is located, the radiofrequencytransponder is spaced from the at least one radially outer edge of theat least one first annular reinforcing ply by at least 10 mm.
 8. Thetire casing according to claim 1, wherein, with the tire casingcomprising at least one second annular rubber mass, coaxial with thereference axis, situated radially externally to the radiofrequencytransponder with respect to the reference axis, with at least one edgesituated in the zone of the tire casing in which the radiofrequencytransponder is located, the radiofrequency transponder is spaced fromthe at least one radially inner edge of the at least one second annularrubber mass by at least 5 mm.
 9. The tire casing according to claim 1,wherein, with the tire casing comprising at least one second annularreinforcing ply, coaxial with the reference axis, situated radiallyexternally to the radiofrequency transponder with respect to thereference axis, with at least one edge situated in the zone of the tirecasing in which the radiofrequency transponder is located, theradiofrequency transponder is spaced from a radially inner edge of theat least one second annular reinforcing ply by at least 10 mm.
 10. Thetire casing according to claim 1, wherein, with the tire casingcomprising at least one third annular reinforcing ply, situated at leastpartly in the crown, coaxial with the reference axis, delineated by twoedges, and comprising metal cords whose main direction is not parallelto the reference axis, the radiofrequency transponder, situated axiallybetween the two edges of the at least one third annular reinforcing ply,is radially spaced from the at least one third annular reinforcing plyby at least 5 mm.
 11. The tire casing according to claim 1, wherein theradiofrequency transponder is encapsulated in at least one electricallyinsulating encapsulating rubber mass.
 12. The tire casing according toclaim 11, wherein an elastic modulus of the encapsulating rubber mass islower than or equal to an elastic modulus of adjacent rubber blends. 13.The tire casing according to claim 11, wherein a relative dielectricconstant of the encapsulating rubber mass is lower than a relativedielectric constant of adjacent rubber blends.
 14. The tire casingaccording to claim 1, wherein the radiofrequency transponderadditionally comprises one or more passive or active electroniccomponents.